Conventionally, various techniques for discriminating whether an object struck by a vehicle is a pedestrian or not have been proposed. For example, disclosed in Japanese Patent Unexamined Publication No. H10-194158 is an object struck discrimination system for discriminating an object struck based on the speed of a vehicle and the acceleration in the forward and rearward directions acting on the vehicle. In such object struck discrimination systems, it is highly demanded to develop a technology for increasing the discrimination accuracy for discriminating an object struck to ensure the protection of a vehicle occupant and/or a pedestrian during a vehicle collision.